1. Field of the Invention
This invention relates to novel and safe multi-component ethylenically unsaturated peroxyester compositions derived from ethylenically unsaturated dicarboxylic acids and methods of preparing them. This invention further relates to using these peroxyester compositions for curing unsaturated polyester resins and for initiating polymerization of ethylenically unsaturated monomers. The present invention also relates to using these peroxyester compositions for preparing polymeric peroxides produced therefrom. The polymeric peroxides derived from the novel and safe ethylenically unsaturated peroxyester compositions of the present invention are effective in preparing graft copolymer compositions having utility in compatibilizing polymeric blends and alloys.
2. Description of the Prior Art
A peroxymonomer, such as a di-t-alkyl diperoxyfumarate (e.g., di-t-butyl diperoxyfumarate), is a valuable composition for preparing a polymeric peroxide. A diperoxyfumarate can copolymerize with another ethylenically unsaturated monomer to form a peroxide-containing copolymer, as well as react with a polymer possessing labile carbon-hydrogen (C--H) bonds to subsequently form a peroxide-containing polymer.
Many newly commercialized polymeric materials are polymeric blends and alloys composed of two or more different polymers. This trend of commercially developing polymeric blends and alloys is attractive because of the ability to develop polymeric blends and alloys that are "tailor made" to meet end-use property specifications, among other reasons. Blending polymers may also result in polymer property improvements including:
(1) better processability; PA1 (2) impact strength enhancement, PA1 (3) improved flame retardance, PA1 (4) improved barrier properties, PA1 (5) improved tensile properties, PA1 (6) improved adhesion, PA1 (7) improved melt flow, PA1 (8) enhanced heat distortion temperature (HDT), PA1 (9) enhanced heat resistance, PA1 (10) improved stiffness, PA1 (11) improved chemical resistance, and PA1 (12) improved ultraviolet light stability.
The major problem encountered in developing new polymeric blends and alloys is the inherent incompatibility or immiscibility of almost all mixtures of two or more polymers. The consequence of incompatibility of polymeric blends and alloys is that they are thermodynamically unstable and, consequently, do not have good mechanical and thermal properties. With sufficient time and temperature, the polymeric blends and alloys generally coalesce into separate phases. An approach used by resin compounders to improve the compatibility of immiscible blends is to use a block or graft copolymer as a compatibilizing agent for the incompatible polymer blend. Generally, block and graft copolymers that are effective compatibilizing agents for polymeric blends and alloys possess at least two unlike polymer segments that are individually compatible with one or the other polymeric component of the polymeric blends and alloys, thereby enabling formation of polymeric blends and alloys having enhanced phase stability.
Low cost polymeric blends and alloys are generally commercially produced from two or more addition polymers, such as polymeric blends comprising low density polyethylene (LDPE), linear low density polyethylene (LLDPE), high density polyethylene (HDPE) and polypropylene (PP). The compatibility of these low cost polymeric blends can be improved by crosslinking the polymeric blends with peroxides or by using compatibilizing block or graft copolymers, as mentioned above.
One important use of a polymeric peroxide, such as a polymer derived from a peroxyfumarate, is in preparing a graft copolymer useful for compatibilizing polymeric blends and alloys. However, there are two major problems encountered in the potential commercialization of di-t-alkyl diperoxyfumarates of the prior art. The first problem is the generally low preparative yields of the di-t-alkyl diperoxyfumarates based upon starting material, for example, fumaryl chloride. The corrected yields for preparing the di-t-butyl diperoxyfumarate and the di-t-amyl diperoxyfumarate are generally about 50-65%, which are quite low. The second problem is the generally extreme hazard of many peroxides, exemplified by the pure diperoxyfumarate derived from lower t-alkyl hydroperoxides. Commercial peroxides react differently and often violently under various hazardous conditions, such as exposure to shock, friction, heat, flame or contamination.
One recognized measure of shock sensitivity is a Trauzl Test Number, derived from a Modified Trauzl Test, as set forth in O. L. Mageli et al., J. Chem. Ed., 48, p. A451 (1971). The Trauzl Number is the cup volume expansion, in milliliters (mL), which is produced when 6 grams (g) of a test specimen is detonated in a heavy lead cup by the shock of a blasting cap. The higher the Trauzl Number, the more forceful the explosion caused by the test specimen. The Trauzl Test Numbers for pure di-t-butyl diperoxyfumarate, pure di-t-amyl diperoxyfumarate and commercial, dry 98% dibenzoyl peroxide are given below:
TABLE 1 ______________________________________ Trauzl Tests - Diperoxyfumarates Peroxide Tested Trauzl Number, mL ______________________________________ Di-t-Butyl Diperoxyfumarate 72 Di-t-Amyl Diperoxyfumarate 49 98% Dibenzoyl Peroxide 28 ______________________________________
The information of Table 1 indicates that pure di-t-butyl diperoxyfumarate and pure di-t-amyl diperoxyfumarate are generally significantly more hazardous than 98% dibenzoyl peroxide. However, of the commercially available organic peroxides, 98% dibenzoyl peroxide has one of the highest Trauzl Numbers. Owing to its high Trauzl Number, 98% dibenzoyl peroxide is restricted to a maximum commercial package size of one pound (i.e., one pound of 98% dibenzoyl peroxide in a paper bag package) due to hazards associated with shipping and handling the 98% dibenzoyl peroxide. In the cases of di-t-butyl diperoxyfumarate and di-t-amyl diperoxyfumarate, the maximum package size would generally have to be restricted to significantly less than one pound. Restricting a peroxide package to such a small size is costly and uneconomical.
Generally, such shipping and handling hazards can be reduced by diluting the hazardous peroxide with a generally high boiling solvent, thereby reducing the relative amount of active diperoxyfumarate used in the composition. However, pure di-t-butyl diperoxyfumarate and pure di-t-amyl diperoxyfumarate are solid materials at room temperature and, at the required storage temperatures, are not readily soluble in the high boiling solvents acceptable to the polymer industry. Generally, solid separation of the pure di-t-butyl diperoxyfumarate and pure di-t-amyl diperoxyfumarate from a solution of the di-t-butyl peroxyfumarate, di-t-amyl diperoxyfumarate and the high boiling solvent occurs, which is highly undesirable.
U.S. Pat. No. 3,536,676 discloses polymerizing di-t-alkyl diperoxyfumarate with monomers such as stryrene, vinyl acetate, vinyl chloride, acrylonitrile, methyl methacrylate and butadiene, at temperatures of about -60.degree. C. to about 80.degree. C. This patent discloses homopolymerization of di-t-butyl diperoxyfumarate which may be carried out as a self-initiated polymerization or using a free radical generating initiator. Yields of the homopolymer are quite low. The patent also discloses copolymerization of di-t-butyl diperoxyfumarate with various ethylenically unsaturated monomors capable of being polymerized by free radical initiation. Although several different copolymerization techniques were used, in general, the yields were low even though the reaction times were long. This patent also discloses the preparation of graft and block copolymers, resin stabilization and resin curing using the disclosed copolymers.
U.S. Pat. No. 3,763,112 discloses preparing polymeric and non-polymeric di-t-alkyl diperoxyfumarate adducts by reacting di-t-alkyl diperoxyfumarate with compounds possessing labile C--H bonds, in the presence or absence of conventional free-radical generators and/or upon exposure to actinic light (visible, ultraviolet, etc.). The results of the reaction which may be simple molecular compounds or polymeric compounds having one or more pendant diperoxysuccinyl groups are of use in preparing block and graft copolymers.
Japanese Patent Application 84/209679 (Chemical Abstracts (hereinafter "CA") 105, (20):173232s (1986)) discloses various OO-t-alkyl O-alkyl monoperoxyfumarates and the use of these monoperoxyfumarates for preparing styrene polymers having enhanced moldability. By virtue of its lower active oxygen content, the OO-t-alkyl O-alkyl monoperoxyfumarate, even when pure, is significantly less hazardous than the comparable di-t-alkyl diperoxyfumarate. However, the pure OO-t-alkyl O-alkyl monoperoxyfumarate is generally difficult and expensive to prepare commercially from fumaric acid or fumaryl chloride. For example, V. V. Shybanov et al., Visn. L'viv. Politekh Inst., 82, pp. 24-27 (1974) (CA, 82, (25):169934m (1975)) discloses the time-consuming and costly stepwise preparation of OO-t-butyl O-alkyl monoperoxyfumarates by adding an alcohol to fumaryl chloride, followed by reacting overnight; lengthy isolation of the resulting intermediate (i.e., alkyl trans-3-chlorocarbonyl-2-propenoate) and subsequent treatment of the intermediate with t-butyl hydroperoxide, followed by reacting overnight and lengthy isolation of the resulting OO-t-butyl O-alkyl monoperoxyfumarate.
Furthermore, when fumaric acid is the starting material, rather than fumaryl chloride, it is necessary to initially synthesize alkyl hydrogen fumarates. Reacting one mole of fumaric acid with one mole of alcohol will produce a mixture of products composed of a dialkyl fumarate, the desired alkyl hydrogen fumarate and unreacted fumaric acid. The unreacted fumaric acid and dialkyl fumarate must be separated from the desired alkyl hydrogen fumarate, which is generally an expensive procedure. The alkyl hydrogen fumarate is then converted to an alkyl trans-3-chlorocarbonyl-2-propenoate via reaction with an acid chlorinating agent. Finally, the alkyl trans-3-chloro-carbonyl-2-propenoate is reacted with a t-alkyl hydroperoxide in the presence of base to give the desired OO-t-alkyl O-alkyl monoperoxyfumarate.
When fumaryl chloride is the starting material, the fumaryl chloride is first reacted with an alcohol to yield an impure mixture containing the desired alkyl trans-3-chlorocarbonyl-2-propenoate. This impure mixture must be purified by a costly distillation process before conducting the next stage of the synthesis process. After purifying the impure mixture by distillation, the alkyl trans-3-chlorocarbonyl-2-propenoate intermediate is reacted with a suspension of an alkali metal salt of a t-alkyl hydroperoxide in a solvent, such as CCl.sub.4, thereby producing the desired OO-t-alkyl O-alkyl monoperoxyfumarate.
Hence, existing techniques of preparing a pure OO-t-alkyl O-alkyl monoperoxyfumarate result in a costly commercial product. Such a product is therefore unlikely to be available for commercially synthesizing a polymeric peroxide which is subsequently used as a graft copolymer compatibilizing agent for polymeric blends and alloys.
British Patent 1,041,088 discloses peroxide-containing copolymer compositions derived from polymerizable ethylenically unsaturated monomers and at least one unit of an unsaturated peroxyester. The ethylenically unsaturated monomers include vinyl esters, esters of acrylic acid and methacrylic acid, vinyl chloride, acrylonitrile, butadiene, isoprene, acrylamide and vinyl ethers, for example. The unsaturated peroxyesters include t-butyl peroxymethacrylate, OO-t-butyl O-hydrogen monoperoxymaleate, OO-t-butyl O-butyl monoperoxymaleate, OO-t-butyl O-butyl monoperoxyfumarate and t-butyl peroxycinnamate, for example. Polymers produced from OO-t-alkyl O-hydrogen monoperoxyfumarates and the OO-t-alkyl O-hydrogen monoperoxymaleates are expected to react at elevated temperatures via non-radical reactions to form non-peroxidic polymers and t-alkyl hydroperoxides.
t-Butyl peroxymethacrylate is difficult to prepare and is hazardous owing to very exothermic self-polymerization/decomposition. t-Butyl peroxycinnamate does not polymerize or copolymerize very readily. As indicated, OO-t-alkyl O-alkyl monoperoxyfumarates, such as OO-t-butyl O-butyl monoperoxy-fumarate, are costly to prepare due to the necessary lengthy and multi-step processes. Therefore, polymeric peroxides produced from the OO-t-alkyl O-alkyl monoperoxyfumarates via free-radical initiated polymerizations are very expensive. The same is true for OO-t-alkyl O-alkyl monoperoxymaleates, such as OO-t-butyl O-butyl monoperoxymaleate.
The novel and safe ethylenically unsaturated peroxyester compositions of the present invention are easy to prepare in better yields than those of the prior art, using a simple and rapid, low-cost process and readily available starting reactants. Therefore, the novel polymeric peroxides derived therefrom will be low in cost.
The multi-component ethylenically unsaturated peroxy ester compositions according to the the present invention overcome the problems of the prior art and are easier to prepare.
Preparations of multi-component compositions of the present invention, such as the combination of dialkyl fumarate, OO-t-alkyl O-alkyl monoperoxyfumarate and di-t-alkyl diperoxyfumarate, via a simultaneous reaction of t-alkyl hydroperoxide and alcohol with fumaryl chloride, in the presence of base, are not reported in the literature. The novel ethylenically unsaturated peroxyester compositions of the present invention are much safer than the prior art di-t-alkyl diperoxyfumarates and are inexpensively prepared in a novel, rapid, low cost process by reacting a mixture of an alcohol and a t-alkyl hydroperoxide with a di-(halocarbonyl) derivative of an ethylenically unsaturated dicarboxylic acid, in the presence of a base. No expensive distillative isolation processes are necessary in the novel processes of the present invention in contrast to the prior art processes.
In addition, the process yields for the novel and safe ethylenically unsaturated peroxyester compositions of the present invention are significantly higher than those of comparable prior art di-t-alkyl diperoxyfumarates. As a result, the peroxyester compositions of the present invention are produced at a generally low cost.